in.] ORGANIC STABILITY. 29 



the shorter diameter of the oval, it stands in its most 

 stable position, and in one from which it is equally diffi- 

 cult to dislodge it by a tilt either forwards or backwards. 

 So long as it is merely tilted it will fall back on being 

 left alone, and its position when merely tilted corre- 

 sponds to a simple deviation. But when it is pushed 

 with sufficient force, it will tumble on to the next 

 edge, B (J, into a new position of stability. It will 

 rest there, but less securely than in its first position ; 

 moreover its range of stability will no longer be dis- 

 posed symmetrically. A comparatively slight push from 

 the front will suffice to make it tumble back, a com- 

 paratively heavy push from behind is needed to make 

 it tumble forward. If it be tumbled over into a 

 third position (not shown in the Fig.), the process 

 just described may recur with exaggerated effect, and 

 similarly for many subsequent ones. If, however, the 

 slab is at length brought to rest on the edge c r>, 

 most nearly corresponding to its longest diameter, the 

 next onward push, which may be very slight, will suffice 

 to topple it over into an entirely new system of stability ; 

 in other words, a "sport" comes suddenly into exist- 

 ence. Or the figure might have been drawn with its 

 longest diameter passing into a projecting spur, so that 

 a push of extreme strength would be required to topple 

 it entirely over. 



If the first position, a b, is taken to represent a type, 

 the other portions will represent sub-types. All the 

 stable positions on the same side of the longer diameter 

 are subordinate to the first position. On whichever of 



